Determination of Al2O3 Activity by Reference Slag Method in CaO-SiO2-Al2O3-MgO Melts for Blast Furnace Slag with High Al2O3 at 1873 K

With the increase in using high Al2O3 iron ore, the content of Al2O3 in blast furnace slag has increased sharply in recent years. Thus, the activity of high Al2O3 slag in the blast furnace slag system needs further study. Herein, the activity of Al2O3 (a(Al2O3)) in CaO-SiO2-Al2O3-MgO slag equilibrated with molten Cu at 1873 K is determined by applying the reference slag method. Isoactivity contours for Al2O3 in the (CaO + MgO)-SiO2-Al2O3 pseudoternary system are achieved for blast furnace slag, and the effects of R (mass% CaO/mass% SiO2) and MgO/Al2O3 on the activity of Al2O3 are discussed. When Al2O3 = 20 wt% and MgO/Al2O3 = 0.4, with R increasing from 1.10 to 1.30, the activity of Al2O3 decreases from 0.0423 to 0.0244. When Al2O3 = 20 wt% and R = 1.25, with MgO/Al2O3 increasing from 0.35 to 0.55, the activity of Al2O3 decreases from 0.0470 to 0.0366. The reference slag method, herein, is feasible based on the experimental results and the reference slag method is simple, reasonable, and of high accuracy.